51 



jection forces out the coloured mass in little drops on the 

 surface of the cord^ and it seems jjrohable that these make 

 their exit by the stomata here described ; but this point could 

 not be distinctly seen. Were this clearly made out, it might 

 at once be concluded that the stomata are the oj^enings of 

 the plasmatic channels ; as it is, the author does not venture 

 to pronounce a positive opinion on this point. 



On a New Species of Gregarina to be called Gregarina 

 GiGANTEA. By Edouard Van Beneden, Doctor of 

 Natural Science, Louvain.^ With Plate VI. 



The little organisms known as Gregarinae have much 

 attracted the attention of naturalists during late years. Their 

 organisation is exceedingly simple ; they consist of merely a 

 single cell, but the history of their development, of their 

 reproduction, and of their metamorphoses, has exercised the 

 sagacity of a great number of eminent observers, and the 

 profusion with which they are spread through nature has 

 caused them to come under the notice of many naturalists. 

 The literature relating to these inferior organisms is very 

 rich, but, nevertheless, several points relating to their organi- 

 sation and to their development are still completely unknown. 



The Gregarinse live as parasites either in the intestine or 

 in the perivisceral cavity, or in the reproductive organs of 

 animals belonging to various classes. They have been pointed 

 out in the various groups forming the class of worms — from 

 the Turbellaria (P. J. Van Beneden and Claparede) and 

 Sagitta (Diesing), as also from the Nematodes (Walter), and 

 the Annelids, where they are extremely abundant. The 

 Gregarinse of the earthworm have chiefly served as the sub- 

 ject for the numerous works of which these animals have 

 been the subject. Schneider has described a species peculiar 

 to the Holothurige ; some are known among Molluscs, even 

 among the Tunicata (Salpa, Diesing). They are very 

 abundant in a great number of insects ; they have been de- 

 scribed as infesting Myriapods ; both Scolopendra, and 

 Julus, and the Crustacea also are sometimes infested with 

 these minute organisms. Cavolini, who was the first to find 

 Gregarinse, observed them in the appendicular organs of the 

 stomach of Cancer depressus ; Von Siebold a long time ago 

 made knoAvn the fine Gregarina of Gammarus Pulex ; Lach- 



^ Read before the Academy of Brussels, and communicated by the author, 



